WO2001065666A1

WO2001065666A1 - Fail-safe mechanism for dc-drive

Info

Publication number: WO2001065666A1
Application number: PCT/DE2001/000592
Authority: WO
Inventors: Harald Witzig
Original assignee: Robert Bosch Gmbh
Priority date: 2000-03-01
Filing date: 2001-02-16
Publication date: 2001-09-07
Also published as: EP1177609A1; US6759823B2; EP1177609B1; US20020105239A1

Abstract

The invention relates to a brushless DC-drive, with a synchronous motor, comprising a multi-phase armature winding (12) and a switch device (11), controlled by an electronic controller (16), connected in series with the armature winding (12) for commutating said armature winding (12). According to the invention, separating means (19) are provided to force a fail-safe operation with simple circuitry and without external components in the armature winding (12), said separating means are activated in case of failure and separate the connections between the winding phases (13), preferably at the star point (20).

Description

FAIL SAFE FOR BRUSHLESS DC POWER DRIVES.

State of the art

The invention is based on a brushless DC drive according to the preamble of patent claim 1.

In vehicles are permanently excited, brushless

DC drives used for a variety of purposes, including for electric power steering. These direct current drives have a synchronous rotor with a stator or armature winding, preferably connected in a star, and a permanently excited rotor. The armature winding is connected to the DC voltage network via a 3-circuit converter with six semiconductor circuit breakers. The inverter, which commutates the armature winding, is controlled by an electronic control unit. An example of a synchronous motor operated on a DC voltage network is shown in DE 37 09 168 AI described.

Occur in the armature winding and / or in the

Circuit breakers fail, so the DC drive can generate a permanent electromagnetic braking torque without a DC voltage being applied, since the synchronous motor now works as a generator against a low-resistance load resistor. In many applications, such a braking torque affects the function of the unit or system in which the DC drive is used. So z. B. in electric power steering, the braking torque occurring in the event of a fault, considerable steering forces to be exerted by the driver, which cannot be accepted. It is therefore known to provide devices on such DC drives which, in the event of a fault, lead to a so-called fail-silent behavior of the DC drive, ie. That is, the DC drive has no disruptive or adverse influence on the unit or the system, so it works as if the drive was not present.

In a known electric power steering, a mechanical clutch is used to generate the desired fail-silent behavior, via which the output shaft of the synchronous motor engages in the steering gear. in the

In the event of a fault, the clutch is opened and the motor is thus disconnected from the steering system. Advantages of the invention

The brushless DC drive according to the invention with the features of claim 1 has the advantage that the desired fail-silent behavior of the DC drive without expensive external components, such as mechanical clutches, is achieved with simple circuit measures in the drive itself. This makes the DC drive more compact and requires less installation space, so that it can be used in a variety of ways. The additional costs that have to be paid for the desired behavior of the DC drive in the event of a fault are significantly reduced.

Advantageous further developments and improvements of the direct current drive specified in claim 1 are possible through the measures listed in the further claims.

According to a preferred embodiment of the invention, the separating means for separating the connections between the development phases of the armature winding can be activated by a control unit which recognizes the fault.

According to an advantageous embodiment of the invention, for this purpose the control unit has measuring shunts arranged in each connecting line between the switching device designed as a bridge circuit with semiconductor switches and the armature winding. The currents flowing over the measuring shunts are measured in simultaneous blocking phases of all semiconductor switches, and if a current value which differs significantly from zero occurs in one of the measuring shunts, the control device issues an activation signal release agents. Such a design of the control unit, with which errors occurring in the switching device are detected, has the advantage that the measuring shunts already present for other reasons for measuring the current in the direct current drive can be used to detect the fault, which further reduces the circuit complexity. Faults in the armature winding itself can e.g. B. detected by measuring the output torque on the output shaft of the synchronous motor, which is advantageous in electric power steering systems, since sensors for measuring the torques occurring on the input and output shafts are already present in the actuators of the electric steering devices.

According to an advantageous embodiment of the invention, in the case of a star connection of the armature winding, the control unit has measuring shunts which each connect a winding phase of the armature winding to the star point. The control unit continuously measures the currents flowing over the measuring shunts according to magnitude and phase and vectorially adds the shunt currents. If the addition result deviates significantly from zero, the control unit sends an activation signal to the separating means. With such a control unit, errors in the semiconductor switching device as well as errors in the armature winding are recognized and the separating means are activated accordingly.

According to advantageous embodiments of the invention, the separating means can be designed in such a way that they irreversibly or reversibly separate the connections between the winding phases of the armature winding. An irreversible separation can be brought about by means of pyrotechnic explosive charges or by means of fuses. Electrical contacts that can be controlled electronically or mechanically are used for the reversible separation. In the case of armature windings in a star connection, the star point is separated; in the case of armature windings in a delta connection, each winding phase must be disconnected from the winding connections.

drawing

The invention is explained in more detail in the following description with reference to exemplary embodiments shown in the drawing. Show it:

1 is a circuit diagram of a brushless DC drive,

Fig. 2 is a circuit diagram of a modified

Armature winding for the direct current drive in FIG. 1,

3 shows a circuit diagram of the armature winding of the direct current drive in FIG. 1 with a modified control unit for actuating separating means for separating the armature winding,

4 each show the same representation as in FIGS. 2 and 5 according to two further exemplary embodiments. Description of the embodiments

The brushless DC drive shown in the basic circuit diagram in FIG. 1 has a synchronous motor which is operated by means of a switching device 11 for electronic commutation at a DC voltage source 10. The synchronous motor shown here only with its stator or armature winding 12 has in a known manner a stator or stator receiving the armature winding 12 and a rotor or rotor rotating in the stator

Permanent magnet poles. In the exemplary embodiment in FIG. 1, the three-phase armature winding 12 has three star-connected winding phases 13, the connections 1, 2 and 3 of which are connected to the switching device 11 via a connecting line 14.

The switching device 11 designed as a B6 inverter has six semiconductor switches 15, preferably MOS-FETS, which are arranged in a bridge circuit. The connecting lines 14 leading to the winding connections 1, 2 and 3 are each connected to the tap 4, 5 and 6 of a bridge branch, each of which is formed by connecting two semiconductor switches 15 in series and which lies in the connection between the two semiconductor switches 15. To commutate the armature winding 12, d. H. For the correct application of the winding phases 13 to the DC voltage source 10, the semiconductor switches 15 can be controlled by an electronic control unit 16.

The brushless DC drive has one

Device for enforcing so-called fail-silent behavior, which ensures that when an error occurs in the DC drive, the z. B. can be caused by a defective semiconductor switch 15 or a winding short in the armature winding 12, the system cooperating with the DC drive is not adversely affected or disturbed. This device comprises separating means which in the event of a fault break the connections between the winding phases 13 and a control unit 17 integrated in the control unit 16 which on the one hand detects the fault and on the other hand activates the separating means when the fault occurs. In the exemplary embodiment in FIG. 1, the control unit 17 includes three measuring shunts, one of which is switched into the three connecting lines 14 between the switching device 11 and the armature winding 12.

The control unit 17 measures the shunt currents flowing over the measuring shunts 18 at time intervals in which all the semiconductor switches 15 are blocked. If all semiconductor switches 15 are intact, each shunt current is zero. If the control unit 17 measures a value deviating significantly from zero in one of the measuring shunts 18, it generates an activation signal which is sent to the separating means and activates them.

In the exemplary embodiment in FIG. 1, the separating means attack in the star point 20 of the armature winding 12 and, when activated, bring about an irreversible separation of the

Star point connection of the winding phases 13. The separating means are designed here, for example, as a pyrotechnic detonator 19, as used, for. B. is used in motor vehicles to trigger the airbags in the event of a crash. The electrically ignitable detonator 19 is connected on the one hand via a connecting line 40 to the control unit 17 and on the other hand to the negative potential of the DC voltage source 10. If one of the measuring shunts 18 delivers a current value that deviates significantly from zero, the control unit 17 generates an electrical ignition pulse which ignites the detonator capsule 19. The exploding explosive charge tears open the star point 20 and the winding phases 13 are separated from one another. As a result, the system-inherent DC drive, which is driven by the system via its output shaft in the event of a fault, cannot generate any braking torque, since the separated armature winding 12 does not permit generator operation.

With the control unit 17 described for FIG. 1, only those errors can be recognized which are based on defects in the semiconductor switches 15. 3, the control unit 17 is modified in such a way that the measuring shunts 18 present in the feed lines 14 are omitted and instead measuring shunts 21 are arranged between the star point 20 and each winding phase 13. The control unit 17 measures the currents flowing through the measuring shunts 21 according to magnitude and phase and adds them vectorially. If the DC motor is fault-free, the addition result always results in zero.

If the vector sum deviates significantly from zero, the control unit 17 in turn generates an activation signal for the separating means which also attack the star point 20. In the embodiment of FIG. 3, the separating means have a fuse 22, which is briefly heated when activated by the control unit 17 so that it melts through and thus separates the star point 20. To heat the fuse 22, a heating coil 24 is used, which is connected to the DC voltage source 10 via a circuit breaker controlled by the control unit 17.

The armature winding 12 of the synchronous motor can of course also be connected in a triangle, for example, as shown in the circuit diagram in FIG. 2. The winding phases 13 are connected to the winding connections 1, 2 and 3. The separating means for separating the winding phases 13 in the event of a fault are integrated in the winding phases 13 and connected in series with them. In the exemplary embodiment in FIG. 2, when released, the separating means cause the armature winding 12 to be reversibly separated

Winding connections 1, 2 and 3 and the winding phases 13 each have an electrical switching contact 23 which can be controlled electronically or mechanically. Electronically controllable switching contacts 23 are implemented, for example, by transistors or thyristors, mechanically controllable switching contacts 23 can be implemented, for example, as an electromagnetic relay.

In the exemplary embodiment in FIG. 4, as in the exemplary embodiment in accordance with FIG. 1, the separating means are arranged at the star point 20 of the armature winding 12 and, when activated, cause the star point 20 to be irreversibly opened. The separating means had two switching contacts 25 biased in the opening direction, each of a holding member 26 set in the closed position are. A switch contact 25 with a holding element 26 is arranged between the star point 20 and the winding end of two winding phases 13. The provision of a third switching contact with a holding element between star point 20 and the third winding phase 13 is not necessary. The two holding members 26 are assigned a common, electronically ignitable, pyrotechnic detonator 27, which is designed so that it can destroy both holding members 26 when triggered. As in the exemplary embodiment in FIG. 1, the detonator 27 is connected via the connecting line 40 to the control unit 17, which in the event of a fault applies an electrical ignition pulse to the detonator 27. When the holding members 26 are destroyed, the prestressed switching contacts 25 are released and open them, so that the connection of the two winding phases 13 to the star point 20 is suddenly interrupted.

In Fig. 4 is a constructive embodiment for the two switch contacts 25 biased in the opening direction with holding member 26 and common detonator 27 for the

Holding members 26 shown schematically. Each switch contact 25 has a contact plate 28 which is fixedly connected to an actuating pin 29. The axially displaceable confirmation pin 29 is loaded by a compression spring 30, which is on the one hand with the

Actuating pin 29 connected spring plate 31 and supported on a fixed stop 32 and biasing the actuating pin 29 so that the contact plate 28 lifts from the contact points 33, 34. The two cold links 26 have a common locking block 35, in which the two actuating pins 29, each with one on the Engage contact plate 28 pioneering end trained locking lug 36. Within the lock block 35, the detonator 27 is arranged, which in their ^τ 0 erriegelungblock the ignition destroyed 35th During assembly, the switching contacts 25 are closed by pressing the contact plate 28 onto the contact points 33, 34 while the compression springs 30 are being tensioned, the locking lug 36 falling into the locking block 35 and being held there. In the event of a fault, the control unit 17 detonates the detonator 27. This destroys the locking block 35, so that the actuating pins 29 are released and the prestressed compression springs 30 lift the contact plates 28 from the contact points 33, 34.

In the exemplary embodiment according to FIG. 5, as in the exemplary embodiment according to FIG. 2, the armature winding 12 is connected in a triangle. Here it is necessary that, in the event of a fault, each branch of the delta connection is disconnected, so that a switching contact 25 with holding element 26 is connected in series with each winding phase 13. in the

5 is assigned to each holding member 26 a separate detonator 27 which, when triggered, destroys the holding member 26, so that the switch contact 25 biased in the closed position opens automatically. Of course, it is also possible to use a common detonator 27 to destroy all three holding members 26. The prestressed switching contacts 25 with the holding member 26 can be designed as described for FIG. 4. When the switching contacts 25 are designed as pretensioned spring tongues, the separate compression springs 30 for opening the switching contacts 25 can be dispensed with.

Claims

claims

1. Brushless DC drive with a multi-phase armature winding (12) ^' having a synchronous motor, with an upstream of the armature winding (12), controlled by an electronic control unit (16) switching device (11) for commutating the armature winding (12) and with a device for generating Fail-silent behavior, characterized in that in the event of a fault, the device has appealing separating means which separate the connections between the winding phases (13) of the armature winding (12;

2. DC drive according to claim 1, characterized in that the separating means by a

Control unit (17) that detects a fault can be activated.

3. DC drive according to claim 1 or 2, characterized in that the separating means are designed so that they cause an irreversible separation.

4. DC drive according to claim 3, characterized in that the separating means have at least one pyrotechnic detonator (19) which can be triggered by the control unit (17).

5. DC drive according to claim 4, characterized in that the. Armature winding (12) is connected in star and the pyrotechnic detonator (19) is arranged at the star point (20) so that it can tear open the star point (20).

6. DC drive according to claim 4, characterized in that the separating means biased switch contacts (25) in the opening direction and each have one of the switch contacts (25) in their closed position fixing holding members (26) and that the at least one detonator (27) is arranged so that it can destroy or detach the holding members (26).

7. DC drive according to claim 6, characterized in that the armature winding (12) connected in star and between the star point (20) and the winding end of at least two winding phases (13) each have a switching contact (25) with holding member (26) and that the two holding members (26) are assigned a common detonator (27).

8. DC drive according to claim 6, characterized in that the armature winding (12) is connected in a triangle and a switching contact (25) with holding member (26) with each winding phase (13) is connected in series and that each holding member (26) has a pyrotechnic Detonator (27) or all holding members (26) are assigned a common detonator (27).

9. DC drive according to claim 3, characterized in that the separating means have at least one of the control unit (17) controllable fuse (22).

10. DC drive according to claim 1 or 2, characterized in that the separating means are designed so that they bring about a reversible separation.

11. DC drive according to claim 10, characterized in that the separating means in the winding phases (13) arranged electrical

Have switching contacts (23) which can be controlled electronically or mechanically.

12. DC drive according to one of claims 9 - 11, characterized in that the armature winding (12) in

Star is switched and the release agent are arranged in the star point (20).

13. DC drive according to one of claims 9 - 11, characterized in that the armature winding (12) in Triangle is connected and the separating means are connected in series with each winding phase (13).

14. DC drive according to one of claims 2-13, characterized in that the switching device (11) has semiconductor switches (15) in a bridge circuit, that the fault-detecting control unit (17) in each connecting line (14) between the switch device (11) and armature winding (12) arranged measuring shunts (18) and that

Control unit (17) measures the currents flowing over the measuring shunts (18) in the simultaneous blocking phases of all semiconductor switches (15) and in at least one of the measuring shunts (18) if a current value which differs significantly from zero occurs

Outputs activation signal to the release agent.

15. DC drive according to one of claims 2-13, characterized in that the fault-detecting control unit (17) has measuring shunts (21), each connecting a winding phase (13) of the armature winding (12) to the star point (20), and that the control unit (17) continuously measures the shunt currents according to magnitude and phase and adds them vectorially and, if the vector sum deviates significantly from zero, gives an activation signal to the separating means.